Molecular cloning, characterization and expression analysis of a putative C-type lectin (Fclectin) gene in Chinese shrimp Fenneropenaeus chinensis.

Lectin is regarded as a potential molecule involved in immune recognition and phagocytosis through opsonization in crustacean. Knowledge on lectin at molecular level would help us to understand its regulation mechanism in crustacean immune system. A novel C-type lectin gene (Fclectin) was cloned from hemocytes of Chinese shrimp Fenneropenaeus chinensis by 3' and 5' rapid amplification of cDNA ends (RACE) PCR. The full-length cDNA consists of 1482 bp with an 861 bp open reading frame, encoding 287 amino acids. The deduced amino acid sequence contains a putative signal peptide of 19 amino acids. It also contains two carbohydrate recognition domains/C-type lectin-like domains (CRD1 and CRD2), which share 78% identity with each other. CRD1 and CRD2 showed 34% and 30% identity with that of mannose-binding lectin from Japanese lamprey (Lethenteron japonicum), respectively. Both CRD1 and CRD2 of Fclectin have 11 amino acids residues, which are relatively invariant in animals' C-type lectin CRDs. Five residues at Ca2+ binding site 1 are conserved in Fclectin. The potential Ca2+/carbohydrate-binding (site 2) motif QPD, E, NP (Gln-Pro-Asp, Glu, Asn-Pro) presented in the two CRDs of Fclectin may support its ability to bind galactose-type sugars. It could be deduced that Fclectin is a member of C-type lectin superfamily. Transcripts of Fclectin were found only in hemocytes by Northern blotting and RNA in situ hybridization. The variation of mRNA transcription level in hemocytes during artificial infection with bacteria and white spot syndrome virus (WSSV) was quantitated by capillary electrophoresis after RT-PCR. An exploration of mRNA expression variation after LPS stimulation was carried out in primarily cultured hemocytes in vitro. Expression profiles of Fclectin gene were greatly modified after bacteria, LPS or WSSV challenge. The above-stated data can provide us clues to understand the probable role of C-type lectin in innate immunity of shrimp and would be helpful to shrimp disease control.

[The application of microsatellite markers for parentage determination in selective breeding of Pacific white shrimp (Litopenaeus vannamei)].

Used simulations and controlled mating to examine the potential of microsatellite markers in assigning parentage to Pacific white shrimp progeny. Cervus simulations demonstrated that the theoretical expectations for parentage exclusion of 10 microsatellite loci and six most polymorphic of the 10 loci were both 0.99, and the assignment success rate of the 6 most polymorphic microsatellite loci set was nearly to 0.97 with 95% confidence. Based on this information, offspring from 10 crosses where parents were known were genotyped by the 6 microsatellite loci and used for parentage analysis. The result showed that assignment success of the progeny to their 'true' mother and father was 88% and 78% respectively, which were lower than predicted by the Cervus simulations. This could be explained by the existence of null or mutant alleles and by Taq DNA Polymerase slippage in the microsatellite loci.

[A preliminary study on the inheritance of microsatellite in two selective breeding families of shrimp (Litopenaeus vannamei)].

Two full-sib families of Litopenaeus vannamei were used to study the inheritance of allelic variation at 10 microsatellite loci. Of the 20 genotypic ratios observed (10 loci x 2 crosses), 17 ratios conformed to Mendelian segregation. When null alleles were considered, one loci (TUMXLv8.220) confirmed Mendelian expectations in all families. While one loci (TUMXLv3.1) showed deviation from family 06. Three loci (TUMXLv5.66,TUMXLv7.74,TUMXLv8.224)were monomorphic in both controlled crosses; 3 loci were polymorphic and confirmed to Mendelian ratios in all families, can be used for parental analysis and population genetic studies. These results indicated the need to test the inheritance pattern for microsatellite markers in shrimp before using them for population genetic or kinship analysis.